﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace just_paly
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello world！！！");
            Console.WriteLine("输入半径r的值");
            string r1 = Console.ReadLine();
            int r = int.Parse(r1);

            double Π = 3.14159265354979;

            int S  =(int)(Π * Π * r);

            Console.WriteLine("面积为"+S);
        }
    }
}
